'Blood Rain' on Spanish Village Remains a Mystery

Here’s one that sounds like a plot line from the upcoming reboot of “The X-Files” — or for a more arcane reference — the files of Charles Fort, the early 20th Century author who collected accounts of bizarre occurrences.

Last year, residents of the Spanish village of Zamora were startled when what looked like raindrops of blood fell from the sky. As the red fluid filled outdoor basins, some people reportedly feared that it was some sort of hazardous chemical that had been dropped from airplanes. Others remembered the Old Testament plagues afflicted upon Egypt.

As news of the strange event got around, a man from a nearby town came to see the blood-colored water for himself, and gathered a sample of it. Over the fall and winter, he kept the blood-colored water and observed it. He noticed that the small particles in the water were staining the containers red. Finally, he sent some of the water to scientists at the University of Salamanca.

When the scientists analyzed the water under a microscope, they quickly deduced what was causing the red liquid. In a newly-published study in Spanish Royal Society of Natural History Journal, they reveal that the culprit is Haematococcus pluvialis, a freshwater green microalgae that’s capable of synthesizing a red carotene pigment called astaxanthin.

But that only solves part of the mystery. Haematococcus pluvialis isn’t usually found in the Mediterranean region, so the scientists aren’t sure how it got into the rainfall over Zamora. Meteorological data analyzed by the scientists suggests that it could have been blown across the ocean by westerly winds, possibly from as far away as North America.

The blood rain is rare, but  isn’t unprecedented. According to an article in the Hindu, an Indian newspaper, since the 1890s there have been sporadic reports of similar rainfall in the south Indian state of Kerala and the neighboring island nation of Sri Lanka, most recently in 2013.

A study published earlier this year in the journal Phylogenetics and Evolutionary Biology pointed to a different microalgae, Trentepohlia annulata, as the source. That species had previously been reported only in Austria. Scientists theorize that it somehow spreads through exchanges between ocean clouds, and that the rain is part of its very weird reproductive process.

From Discovery News